1. Field of the Invention
This invention relates generally to engines for powering machines, especially land vehicles, and more particularly relates to an expansible chamber engine in which each of the chambers is capable of operating in a plurality of different modes, specifically in internal combustion and pneumatic modes.
2. Description of the Related Art
Over the past century, the efforts of many inventors and designers have led to substantial improvements in engines for supplying mechanical power for propelling vehicles, operating industrial machinery and driving other mechanical devices. Although high performance and power were initially of primary interest, in more recent years there has been more emphasis upon improving efficiency in order to gain energy savings and lower pollutant emission for environmental protection purposes.
These more recent design goals typically require that engineering trade-offs must be made in engine design between (1) an engine which exhibits a high fuel efficiency and low pollutant emission; and (2) an engine which is capable of providing high performance and sufficiently high power to meet the power demands of loading under particular conditions, such as high acceleration. Engines for vehicles typically require high performance or power during only a very small proportion of their time of operation and the remainder of the time the engine can exhibit high fuel efficiency and low pollutant emission characteristics. A designer attempts to minimize weight and pollution emission, while maximizing fuel economy, performance and power. Although engines can be designed for very high fuel efficiency and low emission and engines can be designed for high performance and power, once an engine is constructed, the range of variations in these characteristics becomes substantially limited.
One proposed solution, which has recently seen some initial introduction into the commercial market, is the hybrid engine, which couples an internal combustion engine with an electric motor. This type of hybrid engine is capable of changing its mode of operation so that motive power is supplied by the internal combustion engine component or the electric motor component, or both. The electric motor component is designed to also operate as a generator or alternator when driven by the internal combustion engine or during braking.
Although such hybrid IC-electric engines show substantial advantages and promise, they also suffer substantial disadvantages. Electrically powered vehicles require batteries which add substantial weight to a vehicle, thereby reducing fuel efficiency. Additionally, efficiency and fuel economy are deterred by the inefficiency of the process of converting energy from one form to another combined with the need for many such conversions with this type of hybrid engine. The IC and electric hybrid engine requires the chemical energy of the fuel to be converted to heat by combustion, the heat to be converted to mechanical energy by expansion, the mechanical energy to be converted to electrical energy by the generator or alternator and the electrical energy to be converted to chemical energy which is stored in the battery. Then, use of this energy requires that the chemical energy of the battery be converted to electrical energy and the electrical energy be converted in the electric motor to mechanical energy. Each energy conversion step has substantial energy loss and inefficiency inherent in the energy conversion processes.
There have been a variety of systems proposed for recovering energy from the braking of the vehicle. In the hybrid IC-electric engine, the recovery of braking energy is limited by the current capacity of the motor/alternator/generator and also by the battery""s maximum charging rate.
Other inventors have proposed the storage of energy by the use of expansible chamber devices, such as a piston in a cylinder, operated as an air compressor for compressing air into a storage tank. The prior art has also taught the use of compressed air applied to an air motor for a power assist purpose. The prior art teaches the recovery of braking energy by use of an air compressor and the storage of the recovered energy in the form of compressed air. The prior art teaches driving a compressor with an internal combustion engine and the storage of the compressed air. The prior art additionally teaches the use of the compressed air to support combustion in an internal combustion engine.
U.S. patents relevant to this prior art are U.S. Pat. Nos. 4,230,075; 4,290,268; 4,300,486; 3,148,668; 5,549,174; and 3,765,180.
So far as is known, these engine concepts have not received significant commercial research and development, possibly because they, like the hybrid IC and electric engine, require the coupling of at least two separately identifiable engines which introduce the complications of coordinating and controlling their operation.
It is therefore an object and feature of the present invention to improve energy efficiency by reducing the number of conversions of energy from one form to another in order to improve fuel economy.
Another object and feature of the invention is to provide an engine in which the entire engine may be used for all operating conditions, but is capable of optimizing its mode of operation for each operating condition.
Another object and feature of the invention is to minimize engine weight by avoiding the need for batteries and by avoiding the use of multiple, different types of engines or motors coupled together.
Another object and feature of the invention is to improve braking energy recovery by storing all power as mechanical energy in the form of compressed air and using the entire engine for the braking energy recovery, thereby avoiding the electrical current and battery charging rate limitations of electrical systems.
Another object and feature of the invention is to provide a broader range of flexibility in engine characteristics and to minimize the need to sacrifice desirable characteristics as a part of design engineering trade-offs without significantly increased cost of production.
The invention is a hybrid expansible chamber engine, such as a piston and cylinder structure, having a plurality of expansible chamber devices coupled together. Each expansible chamber device is capable of operating in an internal combustion mode, an air motor mode and an air compressor mode. Consequently, the mode for each expansible chamber device can be switched among the available modes to accommodate current operating conditions, as those operating conditions change. This engine operates with known supporting devices such as an air storage tank for compressed air, a fuel source, such as fuel injection, valves and an ignition source. A control system receives input signals, for example representing engine speed, accelerator position and brake pedal position, and from those signals computes and selects the mode of operation for each expansible chamber device so that, at any instant of time, different expansible chamber devices are operating in appropriate modes, which may be different or the same. The combination of modes is changed to most effectively meet presently existing operating conditions as those operating conditions change.